Platelets are essential for staunching blood loss in order for tissue to heal. At a wound site, platelets undergo a coagulation process of activation, shape change, secretion, and aggregation that ultimately leads to a hemostatic clot containing fibrin strands and platelets. Platelets play a unique biomechanical role in hemostasis: their actin-myosin forces strengthen their integrin adhesions and prevent fibrinolysis by pulling fibrin strands and platelets closer together.
Hemodynamics play an important role in the activity of platelets. High shear rate gradients can occur at locations where blood vessels bend, branch, or narrow, and can arise at a vascular stent or artificial valve. These shear gradients have been observed to cause platelets to adhere to the vessel wall, leading to their activation and aggregation. High shear gradients can cause a self-sustaining process where platelet aggregation increases the local shear gradient, further causing platelets to adhere and aggregate.
The primary method by which the body responds to injury is the formation of clots to stop bleeding. The strength of a clot is largely dependent on the ability of platelet cells trapped within it to contract forcefully, which stiffens the fibrin meshwork surrounding the platelets and secures the clot to the wound to prevent rupture. Proper clot formation is critical in trauma patients, since impaired clot formation is associated with a significant increase in mortality. For example, trauma patients with platelet dysfunction can have greater injury severity and worsening shock. They may require more blood transfusions and have greater mortality rates. Patients with such conditions need to be put on more rapid transport from the scene of injury and can be triaged with “damage control” interventions, such as a hypotensive resuscitation strategy. Upon hospital arrival, these patients can be given earlier and more aggressive treatments, including tailored blood product transfusions, and can be more quickly escalated to immediate surgery.
Traditional diagnostic tests that determine whether platelets are adequately coagulating are technically complex and require a significant amount of blood for testing. Further, such tests can take a significant amount of time for a complete reading. This processing time can cause delay in potential treatment techniques for trauma patients, thereby increasing their chance of a negative outcome.